Our comprehensive coverage of the Columbia disaster and its aftermath has been archived.STS-107 Directory

NewsAlert

Sign up for our NewsAlert service and have the latest news in astronomy and space e-mailed direct to your desktop.
Enter your e-mail address:Privacy note: your e-mail address will not be used for any other purpose.

NASA picks shuttle repair techniques for space testsBY WILLIAM HARWOODSTORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSIONPosted: February 10, 2005

After weeks of internal debate, testing and analyses, NASA managers today selected four rudimentary tile and wing leading edge repair techniques to demonstrate during the first post-Columbia shuttle mission.

Two of the repair procedures will be carried out inside the shuttle
Discovery's crew cabin, a so-called "overlay" technique that could prove
useful for fixing damage to heat-shield tiles and a "plug" procedure for
repairing larger holes in wing leading edge panels. A less sophisticated
tile repair technique, one intended for minor damage, will be demonstrated
during a spacewalk, along with a technique for repairing small cracks in
leading edge panels.

A tile repair technique that had long been considered a front runner was
ruled out, however, and while two large backpacks and high-tech caulk guns
will be carried aloft aboard Discovery, they will not be tested in flight,
according to NASA spokesman Kyle Herring.

Instead, engineers will continue work to perfect the technique and if all
goes well it may be tested on the second post-Columbia mission.

Today's Program Requirements Control Board was chaired by shuttle program
manager William Parsons. His decision will be presented to NASA's
Spaceflight Leadership Council a week from Friday for formal approval.

Discovery is scheduled for launch on the first post-Columbia shuttle
mission around May 15. Three spacewalks are planned, two devoted to space
station repair and servicing and one to demonstrate repair procedures. But
technical questions and concerns have held up a decision on which repair
techniques to demonstrate and with time running out to complete crew
training and equipment testing, Parsons, deputy program manager Wayne Hale
and other senior managers heard final presentations today.

Three options were on the table.

The first option called for spacewalkers Stephen Robinson and Soichi
Noguchi to use the cure in-place-ablator applicator - CIPAA - backpacks,
loaded with a tile repair material known as STA-54, to fill in deliberately
damaged tiles in Discovery's cargo bay.

Questions about the reliability of the procedure surfaced last year when
engineers noticed the formation of air bubbles in the viscous STA-54
material as the two compounds that made it up were mixed together in the
backpack. After extensive troubleshooting, engineers were able to reduce the
bubbling but they have not yet eliminated it. The concern is that bubbles
could migrate in weightlessness and form large voids as the material cures.
Those voids could weaken the patch and its ability to shield against
re-entry heating.

A second option debated today called for eliminating a repair
demonstration spacewalk altogether. Instead, the crew would demonstrate the
overlay tile repair procedure in the shuttle's cabin, along with the plug
technique for repairing small holes in leading edge panels. By eliminating
the spacewalk, the crew would have more time for external tile inspections
and logistics transfers to the international space station.

A third option, the one ultimately selected, was chosen because the
techniques in question were the most technically mature and offered the best
opportunity to collect useful in-flight data, Herring said.

Robinson and Noguchi now plan to test a tile repair technique known as
"emittance wash" in Discovery's cargo bay. Using a demonstration kit with
deliberately damaged tiles, the spacewalkers will paint exposed surfaces
with a material that will replace damaged or eroded coating and improve heat
rejection.

Columbia was destroyed two years ago by a hole in a reinforced carbon
carbon wing leading edge panel that hot gas to burn its way into the wing's
interior during re-entry. NASA still has no way to repair that level of
damage, but Robinson and Noguchi will test a rudimentary technique in which
a heat-resistant material known as NOAX will be smoothed over small cracks
in RCC material.

NOAX, which stands for non-oxide adhesive experimental, will be squirted
from a caulk gun-like device and then smoothed out with trowels. The
original procedure required the RCC to be heated prior to NOAX application
and for the patch itself to be heated for a half hour after that to cure the
material. Whether a heater remains part of the new spacewalk demonstration
is not yet known.

Two mechanical fixes that would not be affected by exposure to vacuum
will be tested inside the shuttle's crew cabin, assuming a safety analysis
determines the equipment poses no risk to the astronauts.

The so-called overlay technique for tile repair calls for the astronauts
to cover a panel of damaged tiles with a thin, flexible sheet of
heat-resistant carbon silicon-carbide that would be mounted atop a gasket
and attached with fasteners similar to drywall bolts that would be screwed
into surrounding tile.

The final repair procedure, aimed at fixing small holes in RCC panels,
requires a flexible carbon silicon-carbide patch called a "plug." After fit
checks and application of a sealant, a plug would be inserted into a hole
and held in place from behind by expansion bolts.

Between 20 and 30 different plugs, each with slightly different
geometries, would be needed in a real repair kit to ensure a good fit
virtually anywhere in the curving leading edge.

See the Feb. 6 story for the first take of a detailed overview of all the shuttle in-flight repair options.

Ares 1-X PatchThe official embroidered patch for the Ares 1-X rocket test flight, is available for purchase.U.S. STOREWORLDWIDE STOREApollo CollageThis beautiful one piece set features the Apollo program emblem surrounded by the individual mission logos.U.S. STOREExpedition 21The official embroidered patch for the International Space Station Expedition 21 crew is now available from our stores.U.S. STOREWORLDWIDE STOREHubble PatchThe official embroidered patch for mission STS-125, the space shuttle's last planned service call to the Hubble Space Telescope, is available for purchase.U.S. STOREWORLDWIDE STORE